Picking up new (to Me) Camper next Saturday

After much going back and forth (TT or 5th, Bunks or not)and looking, picked out a 2012 Keystone sprinter 266rbs lastweek and will pick up next weekend. I'm really looking forward to the outside kitchen on this one, which was the deciding factor and hard to find in a 28'ish non bunkhouse. Also has a fold out bed large enough for our 6' teenager who is stil home and camps with us and room for air mattress' if the older two want to join us. A couple of questions.

I never had slides, should I store the camper with the slides out or not?

The previous owner replaced the original fridge and put in an electric only. Can I add an inverter and likely a second battery to run the fridge while traveling?

Any other advice?
Thanks
Joe